148 Professor Dewar [June 1^ 



WEEKLY EVENING MEETING, 



Friday, June 13, 1884. 



Warren De La Rub, Esq. M.A. D.C.L. F.R.S. Manager and Vice- 

 President, in the Chair. 



Professor James Dewar, M.A. F.R.S. M.B.L 



Researches on Liquefied Gases.* 



The two Russian chemists, MM. Wroblewski and Olzewski, who have 

 recently made such a splendid success in the production and main- 

 tenance of low temperature, have used in their researches an enlarged 

 form of the well-known Cailletet apparatus ; but for the purposes of 

 lecture demonstration, which necessarily involves the projection on a 

 screen of the actions taking place, the apparatus represented in the 

 annexed woodcut is more readily and quickly handled, and enables 

 comparatively large quantities of liquid oxygen to be produced. The 

 arrangements will be at once understood on looking at the figure, 

 which is taken from a photograph. The oxygen- or air-reservoir, C, 

 is made of iron ; it contains gas compressed for convenience to 150 

 atmosi)heres. A is the stopcock for regulating the pressure of the 

 gas in the glass tube F, and D is the pressure-manometer, the fine 

 copper tube which connects the gas-reservoir and the glass tube, F, 

 being shown at I. The air-pump gauge is marked J, the tube leading 

 to the double oscillating Bianchi being attached at H. The glass 

 test-tube G, which contains the liquid ethylene, solid carbonic acid, or 

 liquid nitrous oxide, which is to be boiled in vacuo, is placed in the 

 middle of a larger tube. It has holes, shown at E, in the upper part, 

 so that the cool vapours in their course to the air-pump are forced to 

 pass round the outside of the vessel and help to guard it from external 

 radiation. The lower part of the outer cylinder is covered with pieces 

 of chloride of calcium, shown at K. If a thermometer is used and a 

 continuous supply of ethylene maintained, the indiarubber cork 

 through which the tube F passes has two additional apertures for 

 the purpose of inserting the respective tubes. When the pump has 

 reduced the pressure to 25 mm., the ethylene has a temperature of 

 about —140^ C. ; a pressure of between 20 and 30 atmospheres is then 

 sufficient to produce liquid oxygen in the tube F. The tube F is 

 5 mm. in diameter and about 3 mm. thick in the walls, and when 



* See Professor Dewar's discourse on the Liquefaction of Gases. — ' Proceedings ' 

 of the Royal Institution, vol. viii. p. 657. 



